The movement should be a caliber 13ZN. I have seen a similar case before, but I do not know the reference number. However, most collectors would refer to this watch by its caliber (13ZN). Determining the exact year of original invoice would require contacting Longines' Heritage Department, however the watch was likely produced in the early to mid-1940s . Notably, the dial looks original (not refinished), which is important for the value.